Process for producing molded material, molded material, wavefront control element and diffraction grating

Abstract

A process for producing a molded material that can form metallic glass material in a state of lower viscosity, and can manufacture a small structure of several 10 μm or less in a comparatively short time while precisely controlling shape thereof, by the process comprising a heating step of heating supercooled state metallic glass material or a solid metallic glass material at a temperature increase rate of 0.5 K/s to a temperature at or higher than a temperature at which a crystallization process for a supercooled liquid of the metallic glass material begins, and a molding step of transfer molding the metallic glass material until the crystallization process for the supercooled liquid of the metallic glass material has been completed. In addition, the purpose is also to provide the molded material that has been formed by this process, a wavefront control element, and a diffraction grating.

Claims

1. A molded material being a diffraction grating, which comprises a Gd-based, Sm-based, Eu-based, Dy-based, Pt-based, Au-based, Pd-based or Ni-based alloy composition capable of being produced as a metallic glass material and which has on a surface thereof a periodic concavity-convexity having a depth of the concavity being 20 μm or more and not more than 110 μm, and a Period of the concavity-convexity ranging from 0.4 μm to 90 μm, the molded material being produced by a process comprising: a step of heating a supercooled metallic glass material to a temperature which is equal to or higher than a temperature at which a supercooled liquid of the metallic glass material starts to crystallize; and a step of molding the metallic glass material, during the heating step, for a period of time lasting before a completion of a crystallization process of the supercooled liquid of the metallic glass material, into the material having a mixed phase of metallic glass and a crystalline phase or having a crystalline phase alone, wherein the step of heating is performed by beating at a temperature increase rate of 0.5 K/s or more and 5 K/s or less.

2. A molded material in the form of a diffraction grating which comprises a Gd-based, Sm-based, Eu-based, Dy-based, Pt-based, Au-based, Pd-based or Ni-based alloy composition capable of being produced as a metallic glass material and which has on a surface thereof a periodic concavity-convexity having a depth of the concavity being 20 μm or more and not more than 110 μm and a period of the concavity-convexity ranging from 0.4 μm to 90 μm.

3. A wavefront control element comprising the molded material according to claim 2.

4. A molded material being a diffraction grating, which comprises a Gd-based, Sm-based, Eu-based, Dy-based, Pt-based, Au-based, Pd-based or Ni-based alloy composition capable of being produced as a metallic glass material and which has on a surface thereof a periodic concavity-convexity having a depth of the concavity being 20 μm or more and not more than 110 μm, and a period of the concavity-convexity ranging from 0.4 μm to 90 μm, the molded material being produced by a process comprising: a step of heating a solid metallic glass material to a temperature which is equal to or higher than a glass transition temperature of the metallic glass material and is equal to or higher than a temperature at which the metallic glass material starts to crystallize; and a step of molding the metallic glass material, during the heating step, for a period of time starting with an arrival at the glass transition temperature and lasting before a completion of a crystallization process of a supercooled liquid of the metallic glass material, into the material having a mixed phase of metallic glass and a crystalline phase or having a crystalline phase alone, wherein the step of heating is performed by heating at a temperature increase rate of 0.5 K/s or more and 5 K/s or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing relations between metallic glass material states with respect to temperature and elapsed time of heating.

(2) FIG. 2 is (a) a graph that, in heating a metallic glass material, shows a relation between a temperature T and a viscosity coefficient η of the metallic glass material, and (b) a graph that, in heating a metallic glass material, schematically shows a relation between an elapsed time of heating t and a flow amount ΔL of the metallic glass material.

(3) FIG. 3 is a graph that in heating a metallic glass material according to process for producing molded material of an embodiment of the present invention, shows a measurement result of a viscosity coefficient η of the metallic glass material with respect to a temperature T.

(4) FIG. 4 is a side-view showing how transfer molding is performed in a molding step included in process for producing molded material of an embodiment of the present invention.

(5) FIG. 5 shows photomicrographs of diffraction gratings produced according to process for producing molded material of an embodiment of the present invention and using a Gd.sub.60Cu.sub.25Al.sub.15 (at. %) metallic glass material, in which loads applied at the time of transfer molding are (a) 100 MPa and (b) 50 MPa.

(6) FIG. 6 shows an X-ray diffraction spectrum of the molded metal (diffraction grating) shown in FIG. 5(a).

(7) FIG. 7 shows photomicrographs of diffraction gratings produced according to process for producing molded material of an embodiment of the present invention and using a Pt.sub.60Ni.sub.15P.sub.25 (at. %) metallic glass material, in which (a) an average temperature increase rate is 2.5 K/s and a pressure applied at the time of transfer molding is 5 kN, (b) an average temperature increase rate is 3.4 K/s and a pressure applied at the time of transfer molding is 2 kN, and (c) an average temperature increase rate is 3.2 K/s and a pressure applied at the time of transfer molding is 1 kN.

(8) FIG. 8 shows an X-ray diffraction spectrum of the molded metal (diffraction grating) shown in FIG. 7(a).

(9) FIG. 9 shows (a) a photomicrograph and (b) an X-ray diffraction spectrum, of a molded metal (diffraction grating) produced according to process for producing molded material of an embodiment of the present invention and using a Pd.sub.42.5Ni.sub.7.5Cu.sub.30P.sub.20 (at. %) metallic glass material, in which an average temperature increase rate is 5 K/s and a pressure applied at the time of transfer molding is 20 MPa.

(10) FIG. 10 shows (a) a photomicrograph and (b) an X-ray diffraction spectrum, of a molded metal (diffraction grating) produced according to process for producing molded material of an embodiment of the present invention and using a Pd.sub.42.5Ni.sub.7.5Cu.sub.30P.sub.20 (at. %) metallic glass material, in which an average temperature increase rate in laser heating is 1.67 K/s and a pressure applied at the time of transfer molding is 40 MPa.

(11) FIG. 11 shows (a) a photomicrograph and (b) an X-ray diffraction spectrum, of a molded metal (diffraction grating) produced according to process for producing molded material of an embodiment of the present invention and using a Ni.sub.50Pd.sub.30P.sub.20 (at. %) metallic glass material, in which an average temperature increase rate is 0.67 K/s and a pressure applied at the time of transfer molding is 20 MPa.

DESCRIPTION OF EMBODIMENTS

(12) Hereinafter, embodiments of the present invention will be described.

(13) Process for producing molded material of embodiments of the present invention is a process which uses a metallic glass material to produce a molded material, a wavefront control element and a diffraction grating, which are embodiments of the present invention, and the process includes a heating step and a molding step.

(14) The heating step is a step of heating a supercooled metallic glass material or solid metallic glass material to a temperature which is equal to or higher than a temperature at which a supercooled liquid of the metallic glass material starts to crystallize, in which the heating is performed preferably at a temperature increase rate of 0.5 K/s or more.

(15) The molding step is a step performed during the heating step in which the metallic glass material is molded, for a period of time starting with the arrival at the glass transition temperature and lasting before a completion of a crystallization process of the supercooled liquid of the metallic glass material, into a material having a mixed phase of metallic glass and a crystalline phase or having a crystalline phase alone. At this time, the metallic glass material is preferably subjected to transfer molding using a concave-convex mold.

(16) A composition of the metallic glass material is selected preferably considering a target molded material. For the production of G.sub.2 diffraction gratings for neutron beam interferometers, in particular for neutron Talbot interferometers, the metallic glass material is preferably a Gd-based, Sm-based, Eu-based or Dy-based one in view of the capability of Gd, Sm, Eu, Dy to absorb thermal neutrons better than other elements. Such a metallic glass material may be the one that contains at least one component selected from Gd, Sm, Eu and Dy at an atomic ratio of 50% or more and at least one element capable of forming a eutectic crystal together with any of those elements that is selected from, for example, Ag, Al, Au, B, Bi, Cd, Co, Cu, Fe, Ga, Ge, Hg, In, Ir, Mg, Mn, Ni, Pb, Pd, Pt, Rh, Ru, Sb, Si, Sn, Te, Tl, Zn and Zr. Preferred in particular is the addition of B, which is capable of efficiently absorbing neutrons, in an amount not detrimental to the glass formability and the thermal stability at a supercooled liquid state.

(17) For the production of G.sub.2 diffraction gratings for X-ray interferometers, in particular for X-ray Talbot interferometers, for example, the metallic glass material is preferably a Pt-based, Au-based, Pd-based or Ni-based one, in view of the capability of Pt, Au, Pd, Ni to absorb X-rays better than other elements. Such a metallic glass material may be the one that contains at least one component selected from Pt, Au, Pd and Ni at an atomic ratio of 50% or more and at least one component capable of forming a eutectic alloy system together with any of those elements that is selected from, for example, Al, Am, As, B, Be, Bi, Ca, Ce, Cm, Er, Eu, Ga, Gd, Ge, Hf, Ho, In, La, Lu, Nb, Nd, P, Pb, Pr, Sb, Sc, Se, Si, Sn, Sr, Ta, Tb, Te, Th, Ti, Tm, Y, Yb and Zr.

(18) The metallic glass material may take any form: for example, may be composed of a material given by directly supercooling an alloy liquid, or a metallic glass ribbon or metallic glass thin film given by rapidly quenching and solidifying an alloy liquid or by rapidly quenching and solidifying an alloy gas. The metallic glass material may be a metallic glass sheet given by thermal-spraying metallic glass powder prepared by an atomizing method. Crystalline substances with such a size or in such an amount as will not significantly inhibit the viscous flow of the supercooled liquid may be dispersed within the supercooled liquid or within its original metallic glass that has not been heated.

(19) A mold used for the transfer molding in the molding step may be the one that has concavity-convexity arranged either regularly or irregularly. The mold may have concavity and convexity arranged continuously in one direction while having concavity-convexity repeatedly appear in a direction perpendicular thereto, or have convexity-convexity repeatedly in two directions perpendicular to each other. For the production of wavefront control elements and diffraction gratings that have periodic concavity-convexity, use of the mold having periodic concavity-convexity is preferred.

(20) Hereinafter, actions and effects will be described.

(21) The process for producing molded material of an embodiment of the present invention involves heating a supercooled metallic glass material lying under a temperature which is equal to or higher than its glass transition temperature to a temperature which is equal to or higher than its crystallization initiation temperature, and molding the metallic glass material at a lower viscosity, during the heating, for a period of time lasting before the completion of the crystallization process, into the material having a mixed phase of metallic glass and a crystalline phase or having a crystalline phase alone. This configuration enables a highly precise shape control at the time of the molding, giving rise to the molded material with a fine structure measuring not more than tens of micrometers, such as G.sub.2 diffraction gratings for neutron Talbot interferometers and X-ray Talbot interferometers.

(22) The process for producing molded material of embodiments of the present invention requires the metallic glass material to be molded while metallic glass material keeps a supercooled state, which inevitably shortens the production time. According to the process for producing molded material of embodiments of the present invention, increasing a temperature increase rate in the heating step elevates a temperature reached at a supercooled state, which in turn decreases a minimum viscosity coefficient of the metallic glass materials. This configuration enables the metallic glass materials to be molded at a lower viscosity coefficient. Subjecting the metallic glass materials to transfer molding with the use of a mold gives the molded materials a precisely controlled shape. The molded materials are produced with a desired shape in a relatively short period of time.

(23) [Variation of Viscosity Coefficient of Metallic Glass Material During Temperature Increase]

(24) A rapidly-quenched ribbon of metallic glass material Gd.sub.60Cu.sub.25Al.sub.15 (at. %) was subjected to temperature increase at a constant rate of 0.67 K/s, during which the temperature dependence of the viscosity coefficient of the metallic glass material was measured. The measurement result is shown in FIG. 3.

(25) As shown in FIG. 3, the tens-of-K range falling before a minimum viscosity coefficient temperature T.sub.min, although somewhat affected by a viscosity increase observed in the range beginning with T.sub.on, fulfills a relation between reciprocal of temperature (1/T) and a logarithm of viscosity coefficient (log η) that takes a substantially linear form. This means that the temperature dependence of the viscosity coefficient at a supercooled state is as defined in the Arrhenius equation as represented in Formula (3). This verifies the fulfillments of the relations represented by Formula (1) and by FIG. 2 with high precision.

Example 1

(26) The process for producing molded material of an embodiment of the present invention was applied to produce a diffraction grating for neutron beams. A metallic glass material used was a rapidly-quenched ribbon of Gd.sub.60Cu.sub.25Al.sub.15 (at. %). The solid metallic glass material, while being heated at a constant temperature increase rate of not less than 3 K/s to a temperature which is equal to or higher than its crystallization initiation temperature (580 K), was subjected to transfer molding for a period of time starting with the arrival at the glass transition temperature of the metallic glass material and lasting before the arrival at the crystallization completion temperature of the metallic glass material.

(27) The transfer molding was performed with a configuration as shown in FIG. 4: on the surface of a Si wafer 11, a C sheet 12 was put, and thereon a Si mold 13 with concavity-convexity regularly arranged was put such that the concavity-convexity faced upward, and on the mold 13, a metallic glass material 14 ribbon was put, and pressure was applied at the time of molding so as to press the metallic glass material 14 to the mold 13. The same operation was adopted for transfer molding operations carried out in examples provided below.

(28) As shown in FIGS. 5(a) and (b), the transfer molding operations performed with a pressure of 100 MPa and 50 MPa resulted in producing diffraction gratings whose concavity had a depth of 20 μm and 30 μm, respectively. Considering the successful filling to the depth of 30 μm at 50 MPa, the application of 100 MPa would not have been necessarily required for the molding to create a shallow depth of 20 μm, and even the application of 50 MPa would have been sufficient. These diffraction gratings had a pitch between adjacent convexities (width of concavity) of 4 μm and a concavity-convexity period of 9 μm.

(29) FIG. 6 shows the result of an X-ray diffraction of the resultant molded metal (diffraction grating) shown in FIG. 5(a). FIG. 6 verifies the formation of an alloy from the metallic glass raw material. It is considered from the results of FIG. 5 and FIG. 6 that the resultant diffraction gratings having periodic concavity-convexity and composed of a Gd-based alloy are optimal for G.sub.2 diffraction gratings for neutron Talbot interferometers.

Example 2

(30) The process for producing molded material of an embodiment of the present invention was applied to produce a diffraction grating for X-rays. A metallic glass material used was a rapidly-quenched ribbon of Pt.sub.60Ni.sub.15P.sub.25 (at. %). The solid metallic glass material, while being heated at an average temperature increase rate of not less than 2.5 K/s to a temperature (620 to 630 K) higher than its crystallization initiation temperature (570 K), was subjected to transfer molding for a period of time starting with the arrival at the glass transition temperature of the metallic glass material and lasting before the arrival at the crystallization completion temperature of the metallic glass material.

(31) The diffraction gratings produced are shown in FIGS. 7(a)-(c).

(32) FIG. 7(a) shows a diffraction grating that was produced at an average temperature increase rate of 2.5 K/s and at a pressure applied at the transfer molding of 5 kN, and that has concavity whose depth is 100 μm with a pitch between adjacent convexities (width of concavity) being about 10 μm and a concavity-convexity period being about 65 μm. In this instance, a period of time from the initiation of temperature increase until the completion of the transfer molding was about 140 seconds.

(33) FIG. 7(b) shows a diffraction grating that was produced at an average temperature increase rate of 3.4 K/s and at a pressure applied at the transfer molding of 2 kN, and that has concavity whose depth is 50 μm with a pitch between adjacent convexities (width of concavity) being about 20 μm and a concavity-convexity period being about 84 μm. In this instance, a period of time from the initiation of temperature increase until the completion of the transfer molding was about 380 seconds.

(34) FIG. 7(c) shows a diffraction grating that was produced at an average temperature increase rate of 3.2 K/s and at a pressure applied at the transfer molding of 1 kN, and that has concavity whose depth is 50 μm with a pitch between adjacent convexities (width of concavity) being about 8 μm and a concavity-convexity period being about 67 μm. In this instance, a period of time from the initiation of temperature increase until the completion of the transfer molding was about 480 seconds.

(35) FIG. 8 shows the result of X-ray diffraction for the resultant molded metal (diffraction grating) shown in FIG. 7(a). FIG. 8 verifies the formation of an alloy from the metallic glass raw material. It is considered from the results of FIG. 7 and FIG. 8 that the resultant diffraction gratings having periodic concavity-convexity and composed of a Pt-based alloy are optimal for G.sub.2 diffraction gratings for X-ray Talbot interferometers.

Example 3

(36) The process for producing molded material of an embodiment of the present invention was applied to produce a diffraction grating for X-rays. A metallic glass material used was prepared by stacking three rapidly-quenched ribbons of Pd.sub.42.5Ni.sub.7.5Cu.sub.30P.sub.20 (at. %). The solid metallic glass material (thickness: not more than 120 μm), while being heated at an average temperature increase rate of 5 K/s to a temperature (623 K) higher than its crystallization initiation temperature (610 K), was subjected to transfer molding for a period of time starting with the arrival at the glass transition temperature of the metallic glass material and lasting before the arrival at the crystallization completion temperature of the metallic glass material.

(37) The diffraction grating produced is shown in FIG. 9(a). FIG. 9(a) shows that the resultant diffraction grating had concavity whose depth was 60 μm with a pitch between adjacent convexities (width of concavity) being about 5 μm, and a concavity-convexity period being about 10 μm. A pressure at the time of the transfer molding was 20 MPa, and a period of time from the initiation of temperature increase until the completion of the transfer molding was about 180 seconds.

(38) The result of X-ray diffraction for the resultant molded metal (diffraction grating) is shown in FIG. 9(b). FIG. 9(b) verifies the formation of an alloy from the metallic glass raw material. It is considered from the results of FIGS. 9(a) and (b) that the resultant diffraction gratings having periodic concavity-convexity and composed of a Pt-based alloy are optimal for G.sub.2 diffraction gratings for X-ray Talbot interferometers.

Example 4

(39) The process for producing molded material of an embodiment of the present invention was applied to produce a diffraction grating for X-rays. A metallic glass material used was a rapidly-quenched ribbon of Pd.sub.42.5Ni.sub.7.5Cu.sub.30P.sub.20 (at. %) (average thickness: 40 μm). The solid metallic glass material, while being heated by laser at an average temperature increase rate of 1.67 K/s to a temperature (603 K) higher than its crystallization initiation temperature (590 K), was subjected to transfer molding for a period of time starting with the arrival at the glass transition temperature of the metallic glass material and lasting before the arrival at the crystallization completion temperature of the metallic glass material.

(40) The diffraction grating produced is shown in FIG. 10(a). FIG. 10(a) shows that the diffraction grating produced through laser heating had concavity whose depth was 30 μm with a pitch between adjacent convexities (width of concavity) being about 4 μm and a concavity-convexity period being about 10 μm. A pressure applied at the time of the transfer molding was 40 MPa, and a period of time from the initiation of temperature increase until the completion of the transfer molding was about 100 seconds.

(41) The result of X-ray diffraction for the resultant molded metal (diffraction grating) is shown in FIG. 10(b). FIG. 10(b) verifies the formation of an alloy from the metallic glass raw material even in the case of laser heating. It is considered from the results of FIGS. 10(a) and (b) that the resultant diffraction gratings having periodic concavity-convexity and composed of a Pt-based alloy are optimal for G.sub.2 diffraction gratings for X-ray Talbot interferometers.

Example 5

(42) The process for producing molded material of an embodiment of the present invention was applied to produce a diffraction grating for X-rays. A metallic glass material used was a bulk of Ni.sub.50Pd.sub.30P.sub.20 (at. %) (thickness: 1.5 mm, diameter: 30 mm). The solid metallic glass material, while being heated at an average temperature increase rate of 0.67 K/s to a temperature (675 K) higher than its crystallization initiation temperature (668 K), was subjected to transfer molding for a period of time starting with the arrival at the glass transition temperature of the metallic glass material and lasting before the arrival at the crystallization completion temperature of the metallic glass material.

(43) The diffraction grating produced is shown in FIG. 11(a). FIG. 11(a) shows the resultant diffraction grating having a columnar convexity with a diameter of 187 nm on a lattice point of a hexagonal lattice with a length of its one side measuring about 450 nm. A pressure applied at the time of the transfer molding was 20 MPa, and a period of time from the initiation of temperature increase until the completion of the transfer molding was about 180 seconds.

(44) The result of an X-ray diffraction for the resultant molded metal (diffraction grating) is shown in FIG. 11(b). FIG. 11(b) verifies the formation of an alloy from the metallic glass raw material. It is considered from the results of FIGS. 11(a) and (b) that the resultant diffraction gratings having periodic concavity-convexity and composed of a Ni-based alloy are optimal for G.sub.2 diffraction gratings for X-ray Talbot interferometers.

REFERENCE SIGNS LIST

(45) 11: Si wafer 12: sheet 13: mold 14: metallic glass material